Many people have been confused by the term, which during the medieval period is better spelled as "serjant" to make the difference more obvious. Its first use as a term for a military rank is in 1540, so emphatically post-medieval; prior to that time it had a variety of meanings, mainly connected with social status but also sometimes referring to terms such as "serjant at arms" (end of the 14th century) - not a rank but an appointment, just like the terms sheriff, constable and so on.

The original meaning was a servant, either a non-military domestic servant of either gender, or a man serving in a military capacity who was not a knight. This included ordinary civilians carrying out their 40 days of military service as part of their feudal obligations, or as permanent, professional soldiers such as mercenaries, men in a knight's retinue and so on. Serjants held no rank, unless appointed to carry a banner when they would have a specific title such as gounfanouner.

For comparison, the ranks of corporal and lieutenant date from the 1570s, captain is from the 1560s and the rank of colonel is 1540s - so none of them are medieval although the words have older roots. The rank of major is a much later development (1640s).